Comparing Approaches to Optimize Cut-off Scores for Short Cognitive Screening Instruments in Mild Cognitive Impairment and Dementia

BACKGROUND

Although required to improve the usability of cognitive screening instruments (CSIs), the use of cut-off scores is controversial yet poorly researched.

OBJECTIVE

To explore cut-off scores for two short CSIs: the Standardized Mini-Mental State Examination (SMMSE) and Quick Mild Cognitive Impairment (Qmci) screen, describing adjustments in scores for diagnosis (MCI or dementia), age (≤, >75 years), and education (<, ≥12 years), comparing two methods: the maximal accuracy approach, derived from receiver operating characteristic curves, and Youden's Index.

METHODS

Pooled analysis of assessments from patients attending memory clinics in Canada between 1999-2010 : 766 with mild cognitive impairment (MCI) and 1,746 with dementia, and 875 normal controls.

RESULTS

The Qmci was more accurate than the SMMSE in differentiating controls from MCI or cognitive impairment (MCI and dementia). Employing the maximal accuracy approach, the optimal SMMSE cut-off for cognitive impairment was <28/30 (AUC 0.86, sensitivity 74%, specificity 88%) versus <63/100 for the Qmci (AUC 0.93, sensitivity 85%, specificity 85%). Using Youden's Index, the optimal SMMSE cut-off remained <28/30 but fell slightly to <62/100 for the Qmci (sensitivity 83%, specificity 87%). The optimal cut-off for MCI was <29/30 for the SMMSE and <67/100 for the Qmci, irrespective of technique. The maximal accuracy approach generally produced higher Qmci cut-offs than Youden's Index, both requiring adjustment for age and education. There were no clinically meaningful differences in SMMSE cut-off scores by age and education or method employed.

CONCLUSION

Caution should be exercised selecting cut-offs as these differ by age, education, and method of derivation, with the extent of adjustment varying between CSIs.

Validation of the Turkish Version of the Quick Mild Cognitive Impairment Screen

BACKGROUND

The objective of this study was to validate the Turkish version of the Quick Mild Cognitive Impairment (Q mci-TR) screen.

METHODS

In total, 100 patients aged ≥65 years referred to a geriatric outpatient clinic with memory loss were included. The Q mci was compared to the Turkish versions of the standardized Mini-Mental State Examination and the Montreal Cognitive Assessment (MoCA).

RESULTS

The Q mci-TR had higher accuracy than the MoCA in discriminating subjective memory complaints (SMCs) from cognitive impairment (mild cognitive impairment [MCI] or dementia), of borderline significance after adjusting for age and education ( P = .06). The Q mci-TR also had higher accuracy than the MoCA in differentiating MCI from SMC, which became nonsignificant after adjustment ( P = .15). A similar pattern was shown for distinguishing MCI from dementia. Test reliability for the Q mci-TR was strong.

CONCLUSION

The Q mci-TR is a reliable and useful screening tool for discriminating MCI from SMC and dementia in a Turkish population.

Screening for Mild Cognitive Impairment: Comparison of "MCI Specific" Screening Instruments

Background:

Sensitive and specific instruments are required to screen for cognitive impairment (CI) in busy clinical practice. The Montreal Cognitive Assessment (MoCA) is widely validated but few studies compare it to tests designed specifically to detect mild cognitive impairment (MCI).

Objective:

Comparison of two “MCI specific” screens: the Quick Mild Cognitive Impairment screen (Qmci) and MoCA.

Methods:

Patients with subjective memory complaints (SMC; n = 73), MCI (n = 103), or dementia (n = 274), were referred to a university hospital memory clinic and underwent comprehensive assessment. Caregivers, without cognitive symptoms, were recruited as normal controls (n = 101).

Results:

The Qmci was more accurate than the MoCA in differentiating MCI from controls, area under the curve (AUC) of 0.90 versus 0.80, p = 0.009. The Qmci had greater (AUC 0.81), albeit non-significant, accuracy than the MoCA (AUC 0.73) in separating MCI from SMC, p = 0.09. At its recommended cut-off (<62/100), the Qmci had a sensitivity of 90% and specificity of 87% for CI (MCI/dementia). Raising the cut-off to <65 optimized sensitivity (94%), reducing specificity (80%). At <26/30 the MoCA had better sensitivity (96%) but poor specificity (58%). A MoCA cut-off of <24 provided the optimal balance. Median Qmci administration time was 4.5 (±1.3) minutes compared with 9.5 (±2.8) for the MoCA.

Conclusions:

Although both tests distinguish MCI from dementia, the Qmci is particularly accurate in separating MCI from normal cognition and has shorter administration times, suggesting it is more useful in busy hospital clinics. This study reaffirms the high sensitivity of the MoCA but suggests a lower cut-off (<24) in this setting.